This study examines the outcomes of publicly funded methadone maintenance programs treating opiate dependence in Oregon and Washington, two states that include methadone maintenance services in the Medicaid benefit but important differences in financing that have strongly influenced provider practices. We hypothesize that opiate users presenting for treatment in Oregon will have greater access to methadone than their Washington counterparts. Users of methadone maintenance services in Oregon will have greater retention in treatment and subsequently display fewer arrests, less reliance on public assistance, and reduced emergency room visits than their Washington counterparts. Difference in provider policies and practices resulting from both state differences in funding mechanisms will be associated with differences in client outcomes after controlling for client characteristics. The subjects will be Medicaid-eligible opiate users presenting for treatment in Oregon and Washington during 1992 through 2000. Client characteristics and outcomes for 3 years post-admission will be determined from administrative data sets, including statewide treatment databases, Medicaid eligibility files, Medicaid claims/encounter records, statewide arrest databases, quarterly wages, and vital statistics. Provider policies and practices (e.g., dosing and discharge) will be documented through interviews with all methadone providers in both states. A calendar-based protocol will be used to determine how long these have been in place. Our conceptual framework is adapted from Andersen's behavioral model where the use of treatment services and outcomes are a function of both client characteristics and system characteristics driving provider policies and practices. Multilevel analyses using hierarchical linear models (HLM) will be used to address both client and provider or systemic factors. Proximity to a methadone clinic is strongly related to access to methadone maintenance and will be used as an instrumental variable in some analyses.